| | 56 | == Grid ==#Grid |
| | 57 | |
| | 58 | [[Image(Help/MapView:Grid.png,500,link=)]] |
| | 59 | |
| | 60 | A configurable grid can be drawn over the map view, above all layers, as a visual aid: for example to see at a glance which parts of a large area have already been edited, or to lay out a regular street pattern. The grid is purely visual. There is **no snapping** to grid lines; drawing and editing behave exactly as without the grid. |
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| | 62 | Show and hide:: [wikitr:/Help/Menu/View View] > **Grid** > **Show**. The action can also be placed on the [wikitr:/Help/Preferences/Toolbar toolbar]. |
| | 63 | Settings:: [wikitr:/Help/Menu/View View] > **Grid** > **Grid preferences...** opens [wikitr:/Help/Preferences/Grid Preferences > Grid] directly: grid type (projected coordinates in metres, or latitude/longitude in degrees), east and north spacing, rotation, origin, line width, blend mode and the minimum distance of the lines on screen. The line colors are in [wikitr:/Help/Preferences/Colors Preferences > Colors] ("grid east lines", "grid north lines"). |
| | 64 | |
| | 65 | The default is a grid of 1000 m × 1000 m in projected coordinates, drawn in yellow with the "hard light" blend mode so that it stays visible over light and dark map features. Spacings of a projected grid are true distances in metres, the same as measured by the [wikitr:/Help/Action/Parallel parallel way tool] and the status bar. When zooming out, the spacing is automatically multiplied by 10 (100, 1000, ...) as soon as the lines would come closer than a configurable number of pixels, so the grid stays readable while remaining aligned to the configured one. |
| | 66 | |
| | 67 | **Latitude/longitude grid and the world bounds:** when zoomed out far enough that the edge of the projection's usable area (e.g. ±85° latitude for the default Mercator projection) becomes visible, the meridians stop at that edge instead of continuing to the pole. This is correct: it is the same limit the projection itself, the downloaded data and the background imagery are subject to, not a defect of the grid. |
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| | 69 | === Placing the grid from the current selection === |
| | 70 | |
| | 71 | Two entries of [wikitr:/Help/Menu/View View] > **Grid** position the grid from the current selection in the data layer, without typing coordinates: |
| | 72 | |
| | 73 | Set origin to selection:: Moves the grid so that a north-south and an east-west line cross at the selected point, and switches the grid on. Select a single node (for example a street intersection) to use its exact position; with any other selection (several nodes, one or more ways, a relation) the origin is the centroid — the arithmetic mean position of every node reachable from the selection. For a projected grid the origin is also the point at which the metric spacing is exact, so pick a point inside the area you work in. The entry is disabled while the selection contains no node with known coordinates. |
| | 74 | Align rotation to selection:: Rotates the grid so that its lines run parallel to the current selection: either a single way (direction from its first to its last node) or exactly two nodes. Select a long, straight stretch of one of the streets first. The grid is switched to projected coordinates (a latitude/longitude grid cannot be rotated) and switched on. The entry is disabled while the selection does not define a direction. |
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| | 76 | Both entries follow the selection live, so they enable and disable themselves as you select and deselect objects; there is no need to reopen the menu. |
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| | 78 | Typical workflow for an existing regular street grid: select a straight main street, View > Grid > **Align rotation to selection**; then select the node at a street intersection, View > Grid > **Set origin to selection**; finally set the block size as spacing via View > Grid > **Grid preferences...**. |
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| | 80 | === Tile borders of imagery layers === |
| | 81 | |
| | 82 | Independent of the grid, imagery layers can draw a thin border around each of their tiles: right click on the map (or on the layer in the [wikitr:/Help/Dialog/LayerList layer list]) and check **Show tile borders**. This helps to tell which tile is being looked at, for example together with **Show tile info**. The setting applies to that layer and is stored with it in [wikitr:/Help/Action/SessionSave sessions]; switching it on or off is also remembered, so layers opened later and after a restart of JOSM follow the last choice. Its color is "imagery tile border" in [wikitr:/Help/Preferences/Colors Preferences > Colors]. |
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